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Nacre in Molluscs from the Ordovician of the Midwestern United States
Department of Biological Science (MH-282), California State University, Fullerton, CA 92834, USA
Department of Stratigraphy and Palaeontology, Faculty of Sciences, University of Granada, Avenida Fuentenueva s/n, Granada 18071, Spain
Dry Dredgers, 1621 Westwood Avenue, Cincinnati, OH 45214, USA
Midwest Institute of Geosciences and Engineering, 2328 West Touhy Avenue, Chicago, IL 60645, USA
* Author to whom correspondence should be addressed.
Received: 13 November 2012; in revised form: 24 December 2012 / Accepted: 31 December 2012 / Published: 8 January 2013
Abstract: Nacre was previously thought to be primitive in the Mollusca, but no convincing Cambrian examples are known. This aragonitic microstructure with crystal tablets that grow within an organic framework is thought to be the strongest, most fracture-resistant type of shell microstructure. Fossils described herein from the Ordovician of Iowa, Indiana, and Ohio provide supporting evidence for the hypothesis that sometime between the middle Cambrian and late Ordovician, nacre originated in cephalopod, bivalve, and possibly gastropod lineages. The correlation of independent origins of fracture-resistant nacre with increasing shell-crushing abilities of predators during the Cambrian-Ordovician suggests an early pulse in the evolutionary arms race between predators and molluscan prey.
Keywords: nacre; Ordovician; Isorthoceras; cephalopod; shell microstructure; Maquoketa; Arnheim; Cyclora; Ohio; Iowa
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Vendrasco, M.J.; Checa, A.; Heimbrock, W.P.; Baumann, S.D. Nacre in Molluscs from the Ordovician of the Midwestern United States. Geosciences 2013, 3, 1-29.
Vendrasco MJ, Checa A, Heimbrock WP, Baumann SD. Nacre in Molluscs from the Ordovician of the Midwestern United States. Geosciences. 2013; 3(1):1-29.
Vendrasco, Michael J.; Checa, Antonio; Heimbrock, William P.; Baumann, Steven D. 2013. "Nacre in Molluscs from the Ordovician of the Midwestern United States." Geosciences 3, no. 1: 1-29.